Sewing · fabric yardage
Circle skirt fabric calculator.
Enter your waist, skirt length and fabric width. Get the waist radius, the two radii to mark, the cut layout and the fabric to buy in metres and yards, for a full, half, quarter or double circle. Runs in your browser; nothing is sent or stored.
Skirt and fabric
Radii, layout and yardage
Worked example
A full circle skirt, 70 cm waist, 60 cm long, 1.5 cm seams, 1 cm hem, on 140 cm fabric. Waist radius r = 70 / (2 x pi) = 11.14 cm. Cut the waist hole at r minus the seam allowance, 11.14 - 1.5 = 9.64 cm. The outer cut radius is R = 11.14 + 60 + 1 = 72.14 cm, so one whole disc would be 144.28 cm across, wider than the fabric. The calculator then tries two half circles (each 147.28 x 75.14 cm with seam allowance), and finds the shortest fit is 2 pieces stacked, about 2.95 m (3.2 yd) of 140 cm fabric. A 150 cm fabric would let one disc lie flat with no centre seam, at about 1.44 m.
How it is calculated
Waist radius. The circumference of a circle is 2 x pi x r, and a sector of angle theta (in radians) has an arc of theta x r. The waist edge is that arc, so r = waist / theta. Theta is 2 x pi for a full circle, pi for a half, pi/2 for a quarter and 4 x pi for a double circle (two full circles cut open and joined, so the waist arc is twice a full circle).
Cut radii. Inner (waist hole) = r - seam allowance; outer (hem) = r + length + hem allowance. Mark each as an arc with a string or tape pivoting at the centre point.
Layout. The skirt can be cut as 1, 2, 4, 8 or 16 equal sectors (only counts that divide the total angle). Each sector is boxed in a rectangle: width and height R for 90 degrees or less (R by R x sin of the angle), R x (1 - cos of the angle) by R between 90 and 180 degrees, and 2R by 2R for a whole disc. Every cut (radial) edge adds a seam allowance on each side of that box. Boxes are packed in rows across the usable width in whichever orientation is shorter, and the shortest total length that fits is shown. Boxes ignore the empty waist hole and interlocking between wedges, so real nesting can be a little tighter. Buy extra for matching, nap and shrinkage.
Yardage. Length in metres is the layout length rounded up to the next 0.1 m; yards is the length in inches divided by 36, rounded up to the next 1/8 yd.
Sources. Circle circumference and arc: Wolfram MathWorld, Circle. Sector arc length and angle: Wolfram MathWorld, Circular Sector. No tables or rates are used. As of 2026-10-02 the double circle meaning (720 degrees of waist arc) is this calculator's stated convention; patterns that call a skirt "double circle" are not all consistent, so check yours.
Boundary: this estimates fabric for a plain unlined skirt. It does not include a waistband, lining, pockets, a pile or print repeat, or fabric lost to a one-way nap. Dress-forms and bias hang vary; test with a cheap fabric if the cut is expensive.
Frequently asked questions
How do you calculate the waist radius of a circle skirt?
The waist edge is an arc of the circle, so waist = angle x radius, with the angle in radians. A full circle spans 2 x pi, so r = waist / 6.283. A half circle spans pi (r = waist / 3.142), a quarter circle spans pi/2 (r = waist / 1.571) and a double circle spans 4 x pi (r = waist / 12.566). The calculator then subtracts your waist seam allowance to get the radius of the hole you actually cut.
How much fabric do I need for a circle skirt?
It depends on the length, the waist and above all the usable fabric width. The outer cut radius is R = waist radius + skirt length + hem allowance, and a full circle needs a square at least 2R on each side. If 2R is wider than your fabric, the skirt is cut in two or more sectors and the length grows. Enter your numbers and the calculator tries every split (1, 2, 4, 8 or 16 sectors) and shows the shortest one that fits.
What is the difference between full, half, quarter and double circle skirts?
They differ in how much waist arc the skirt is spread over: 360, 180, 90 or 720 degrees. A full circle is the usual swirly skirt, a half circle is flatter with less volume and uses less fabric, a quarter circle is close to an A-line with a very large waist hole, and a double circle is the fullest. The double circle here means two full circles cut open and joined, so its waist arc is 720 degrees.
Why should a circle skirt hang before hemming?
Parts of the hem run along the bias of the weave, which stretches under the skirt's own weight, so the hem can drop unevenly. The usual advice is to let the cut skirt hang for a day, then trim the hem level before folding it up. The hem allowance in this calculator is the amount folded under, so the fabric length it shows does not include the extra you may trim off.
Does a circle skirt need a zipper?
Only if the waist opening is smaller than your hips. The waist radius here is calculated for the waist measurement you enter, so a skirt with no opening has to be big enough to pull over your hips. If it is not, add a zipper or a wrap or button opening. A half or quarter circle has a built-in seam where an opening can go.
Why does the calculator show more fabric than a pattern envelope?
It uses rectangular bounding boxes for each piece with a seam allowance on every cut edge, so it will overestimate slightly against a hand-nested layout. Add extra for pattern matching, a one-way print or nap, shrinkage from pre-washing, and mistakes. Check the cut diagram before you buy.